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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Miscompile of spec2006/perlbench"
href="https://llvm.org/bugs/show_bug.cgi?id=31449">31449</a>
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<th>Summary</th>
<td>Miscompile of spec2006/perlbench
</td>
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<th>Product</th>
<td>new-bugs
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>Other
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>mssimpso@codeaurora.org
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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<pre>Top-of-trunk is currently miscompiling spec2006/perlbench on AArch64 for "-O1"
and above. For example, with "clang -target=aarch64-linux-none-gnu -O2 ...".
I've bisected the miscompile to:
commit 7b626dfd628404afb5fb410e8cb9eedf8e1722b4
Author: Ehsan Amiri <<a href="mailto:amehsan@ca.ibm.com">amehsan@ca.ibm.com</a>>
Date: Thu Dec 15 12:25:13 2016 +0000
[InstCombine] New opportunities for FoldAndOfICmp and FoldXorOfICmp
A number of new patterns for simplifying and/xor of icmp:
(icmp ne %x, 0) ^ (icmp ne %y, 0) => icmp ne %x, %y if the following is true:
1- (%x = and %a, %mask) and (%y = and %b, %mask)
2- %mask is a power of 2.
(icmp eq %x, 0) & (icmp ne %y, 0) => icmp ult %x, %y if the following is true:
1- (%x = and %a, %mask1) and (%y = and %b, %mask2)
2- Let %t be the smallest power of 2 where %mask1 & %t != 0. Then for any
%s that is a power of 2 and %s & %mask2 != 0, we must have %s <= %t.
For example if %mask1 = 24 and %mask2 = 16, setting %s = 16 and %t = 8
violates condition (2) above. So this optimization cannot be applied.
git-svn-id: <a href="https://llvm.org/svn/llvm-project/llvm/trunk@289813">https://llvm.org/svn/llvm-project/llvm/trunk@289813</a>
91177308-0d34-0410-b5e6-96231b3b80d8</pre>
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